System and method for segmentation of lung

ABSTRACT

Disclosed are systems, devices, and methods for determining pleura boundaries of a lung, an exemplary method comprising acquiring image data from an imaging device, generating a set of two-dimensional (2D) slice images based on the acquired image data, determining, by a processor, a seed voxel in a first slice image from the set of 2D slice images, applying, by the processor, a region growing process to the first slice image from the set of 2D slice images starting with the seed voxel using a threshold value, generating, by the processor, a set of binarized 2D slice images based on the region grown from the seed voxel, filtering out, by the processor, connected components of the lung in each slice image of the set of binarized 2D slice images, and identifying, by the processor, the pleural boundaries of the lung based on the set of binarized 2D slice images.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/124,371, filed on Sep. 7, 2018, which is a continuation of U.S.patent application Ser. No. 15/808,975, filed on Nov. 10, 2017, now U.S.Pat. No. 10,074,185, which is a continuation of U.S. patent applicationSer. No. 14/754,867, filed on Jun. 30, 2015, now U.S. Pat. No.9,836,848, and entitled “SYSTEM AND METHOD FOR SEGMENTATION OF LUNG,”which claims the benefit of and priority to U.S. Provisional PatentApplication Ser. No. 62/020,261 filed on Jul. 2, 2014, the entirecontents of each of which are incorporated herein by reference.

BACKGROUND Technical Field

The present disclosure relates to systems and methods for segmentationof a lung. More particularly, the present disclosure relates to systemsand methods that defines the borders of the lung based on athree-dimensional (3D) model generated based on CT scan image data of apatient's chest.

Discussion of Related Art

A patient's lungs are located within a thoracic cavity, which isseparated from the abdominal cavity by the muscular diaphragm located atthe base of the lungs. Further, the lungs are surrounded by adouble-walled sac called the pleura (visceral pleurae and parietalpleurae) and a pleural fluid between the pleura and the lungs. Thepleural fluid enables the lungs to expand and contract without adheringthe pleura.

Visualization techniques related to visualizing the lungs have beendeveloped so as to help clinicians to perform diagnoses, surgeriesand/or other treatment procedures. Visualization is especially importantfor identifying a location of a diseased region having correspondingsymptoms. Further, when treating the diseased region, additionalemphasis is given to identification of a correct location so that aproper procedure is performed at the correct location. Furthermore,visualization of borders of the lungs are critical because diseasedregions and locations for surgical operations should be within theborders of the lungs. Thus, visualization of pleura is important becausethe pleura define the borders of the lungs.

SUMMARY

Provided in accordance with the present disclosure is a method fordetermining pleura boundaries of a lung.

In an aspect of the present disclosure, a segmentation method comprisesacquiring image data from an imaging device, generating a set oftwo-dimensional (2D) slice images based on the acquired image data,determining, by a processor, a seed voxel in a first slice image fromthe set of 2D slice images, applying, by the processor, a region growingprocess to the first slice image from the set of 2D slice imagesstarting with the seed voxel using a threshold value, generating, by theprocessor, a set of binarized 2D slice images based on the region grownfrom the seed voxel, filtering out, by the processor, connectedcomponents of the lung in each slice image of the set of binarized 2Dslice images, and identifying, by the processor, the pleural boundariesof the lung based on the set of binarized 2D slice images.

In another aspect of the present disclosure, the seed voxel is in aportion of the first slice image from the set of binarized 2D sliceimages corresponding to a trachea of the lung.

In yet another aspect of the present disclosure, the threshold value isgreater than or equal to an intensity of the seed voxel.

In a further aspect of the present disclosure, the acquired image datais stored in the digital imaging and communications in medicine (DICOM)image format.

In another aspect of the present disclosure, the image data is acquiredvia a network device.

In a further aspect of the present disclosure, applying the regiongrowing process includes in a case where an intensity of a first voxelin the first slice image from the set of 2D slice images is lower thanthe predetermined threshold value and the first voxel is connected tothe seed voxel, setting the intensity of the first voxel as a maximumvalue, and in a case where an intensity of a second voxel in the firstslice image from the set of 2D slice images is not lower than thepredetermined threshold value or the first voxel is not connected to theseed voxel, setting the intensity of the second voxel as a minimumvalue.

In another aspect of the present disclosure, the threshold value causesa high intensity area to appear around the seed voxel in the set of 2Dslice images.

In a further aspect of the present disclosure, applying the regiongrowing process further includes inversely assigning values of voxels inthe set of 2D slice images, from the minimum value to the maximum valueand from the maximum value to the minimum value, to obtain the set ofbinarized 2D slice images.

In another aspect of the present disclosure, filtering out connectedcomponents of the lung includes detecting a connected component in theset of binarized 2D slice images, calculating an area of each connectedcomponent in the set of binarized 2D slice images, determining whetherthe area of each connected component is less than a predetermined value,assigning the minimum value to pixels of a first connected componentwhen it is determined that an area of the first connected component isless than the predetermined value, and assigning the maximum value topixels of a connected component when it is determined that an area ofthe second connected component is greater than or equal to thepredetermined value.

In a further aspect of the present disclosure, a connected component isan enclosed area with high intensity.

In another aspect of the present disclosure, the connected component isa blood vessel or an airway.

In a further aspect of the present disclosure, an intersection of three2D slice images, each of which is from each of three independentdirections, identifies a voxel in the set of 2D slice images.

In another aspect of the present disclosure, the three independentdirections are axial, coronal, and sagittal directions.

In a further aspect of the present disclosure, each voxel of the set ofbinarized 2D slice images has either high or low intensity.

In another aspect of the present disclosure, the image data is acquiredfrom computed tomographic technique, radiography, tomogram produced by acomputerized axial tomography scan, magnetic resonance imaging,ultrasonography, contrast imaging, fluoroscopy, nuclear scans, andpositron emission tomography.

In another aspect of the present disclosure, a system for determiningpleura of a lung comprises an imaging device configured to image a chestof a patient to obtain image data, and an image processing deviceincluding a memory configured to store data and processor-executableinstructions, and a processor configured to execute theprocessor-executable instructions to generate a set of two-dimensional(2D) slice images based on the acquired image data, determine a seedvoxel in a first slice image from the set of 2D slice images, apply aregion growing process to the first slice image from the set of 2D sliceimages starting with the seed voxel using a threshold value, generate aset of binarized 2D slice images based on the region grown from the seedvoxel, filter out connected components of the lung in each slice imageof the set of binarized 2D slice images, and identify the pleuralboundaries of the lung based on the set of binarized 2D slice images.

Any of the above aspects and embodiments of the present disclosure maybe combined without departing from the scope of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

Objects and features of the presently disclosed systems and methods willbecome apparent to those of ordinary skill in the art when descriptionsof various embodiments are read with reference to the accompanyingdrawings, of which:

FIG. 1 is a schematic diagram of an example device which may be used forsegmenting computed tomography (CT) image data of a patient's lungs, inaccordance with an embodiment of the present disclosure;

FIG. 2A is a graphical illustration of 2D images identifying a voxel forsegmentation with the lung area shown in black, in accordance with anembodiment of the present disclosure;

FIG. 2B is a graphical illustration of 2D images identifying a voxel forsegmentation with the lung area shown in white, in accordance with anembodiment of the present disclosure;

FIG. 3 is a graphical illustration of 2D images identifying a voxel forsegmentation with the lung area shown in grey, in accordance with anembodiment of the present disclosure;

FIGS. 4A-4B are graphical illustrations of a filtering process ofconnected components in 2D images of a patient's lungs, in accordancewith an embodiment of the present disclosure;

FIG. 5A is a flowchart illustrating an example method for segmenting 2Dimages of a patient's lungs to define the pleura boundary of patient'slungs, in accordance with an embodiment of the present disclosure;

FIG. 5B is a flowchart illustrating an example method for applying aregion growing process, in accordance with an embodiment of the presentdisclosure; and

FIG. 5C is a flowchart illustrating an example method for filtering outconnected components, in accordance with an embodiment of the presentdisclosure.

DETAILED DESCRIPTION

The present disclosure is related to systems and methods for segmentingimage data of a patient's chest to identify the pleural boundaries ofthe patient's lungs.

Segmenting image data of a patient's chest to identify the pleuralboundaries of the patient's lungs may be a necessary component of anELECTROMAGNETIC NAVIGATION BRONCHOSCOPY® (ENB) procedure using anelectromagnetic navigation (EMN) system. An ENB procedure generallyinvolves at least two phases: (1) planning a pathway to a target locatedwithin, or adjacent to, the patient's lungs; and (2) navigating a probeto the target along the planned pathway. An example of the planningsoftware described herein can be found in U.S. Pat. Nos. 9,459,770,9,925,009, and 9,639,666, all of which are filed by Covidien LP on Mar.15, 2013 and entitled “Pathway Planning System and Method,” all of whichare incorporated herein by reference. An example of the planningsoftware can be found in commonly assigned U.S. Pat. No. 9,770,216entitled “SYSTEM AND METHOD FOR NAVIGATING WITHIN THE LUNG” the entirecontents of which are incorporated herein by reference.

Prior to the planning phase, the patient's lungs are imaged by, forexample, a computed tomography (CT) scan, although additional applicablemethods of imaging will be known to those skilled in the art. The imagedata assembled during the CT scan may then be stored in, for example,the Digital Imaging and Communications in Medicine (DICOM) format,although additional applicable formats will be known to those skilled inthe art. The CT scan image data may then be loaded into a planningsoftware application (“application”) to be processed for generating a 3Dmodel which may be used during the planning phase of the ENB procedure.Segmenting image data of the patient's chest may be a component of theprocess of generating the 3D model, or may be performed separately.

The application may use the CT scan image data to generate a 3D model ofthe patient's lungs. The 3D model may include, among other things, amodel airway tree corresponding to the actual airways of the patient'slungs, and showing the various passages, branches, and bifurcations ofthe patient's actual airway tree. While the CT scan image data may havegaps, omissions, and/or other imperfections included in the image data,the 3D model is a smooth representation of the patient's airways, withany such gaps, omissions, and/or imperfections in the CT scan image datafilled in or corrected. After it is generated, the 3D model may bepresented in various views. Although the present disclosure will bedescribed in terms of specific illustrative embodiments, it will bereadily apparent to those skilled in this art that variousmodifications, rearrangements and substitutions may be made withoutdeparting from the spirit of the present disclosure. The scope of thepresent disclosure is defined by the claims appended hereto.

FIG. 1 shows an image processing device 100 that may be used forsegmentation of the lungs. Device 100 may be a specialized imageprocessing computer configured to perform the functions described below.Device 100 may be embodied in any form factor known to those skilled inthe art, such as, a laptop, desktop, tablet, or other similar computer.Device 100 may include, among other things, one or more processors 110,memory 120 storing, among other things, the above-referenced application122, a display 130, one or more specialized graphics processors 140, anetwork interface 150, and one or more input interfaces 160.

The CT scan image data may be stored in the memory 120 in the DICOMformat. A set of 2D slice images may be generated based on the CT scanimage data. In an aspect, the 2D slice images may be generated to depictthe axial, coronal, and sagittal views of the patient at a givenlocation. For example, at each intersecting point of the chest, theremay be three different 2D slice images generated in the threeindependent directions. These 2D slice images may be loaded intoapplication 122 which is executed by processors 110 to reformat the 2Dslice images for display. For example, application 122 may convert acolor space of the 2D slice images to another color space suitable fordisplay and perform imaging processes, e.g., scale, rotation,translation, or projection, to display the 2D slice images as intended.Based on at least three different 2D slice images, a voxel may beidentified. The 2D slice images may be processed using a region growingalgorithm to distinguish different types of tissue and materials toidentify the pleural boundaries of the lungs. A variety of regiongrowing algorithms are known in the art. Memory 120 may also storeapplications that may generate the 3D model of the chest or that mayidentify the pleural boundaries of the lungs.

FIG. 2 illustrates three 2D slice images identifying a seed voxel 220,which is identified as a pixel from each 2D slice image (205, 210, 215)which define the voxel for segmentation in accordance with an embodimentof the present disclosure. As shown in FIG. 2, seed voxel 220 isidentified at an intersecting point in the trachea of a patient wherethe three 2D slice images intersect with each other. Segmentation is animage processing step that partitions the set of 2D slice images basedon a Hounsfield value assigned to a voxel in the set of 2D slice images,and is used for defining difference in the intensity of the images inorder to more clearly define organs and other varying intensity aspectsof the images and, in embodiments of the present disclosure, the pleuralboundaries of the lungs.

In one embodiment, segmentation may be used to distinguish an insidearea of the lungs from an outside area of the lungs in the set of 2Dslice images. Segmentation may include binarization where the 2D sliceimages are displayed with only two different intensity values, andfiltering processes as will be described in greater detail below.

As a first step of the present disclosure, a set of 2D slice images isgenerated from CT scan image data of the patient's chest. Once the setof 2D slice images is generated, a seed voxel 220 must be selected. FIG.2A depicts a manual process whereby the seed voxel 220 is shown beingselected in the 2D slice images. Three 2D slice images 205, 210, and 215depict the chest of a patient along each of the axial, sagittal, andcoronal directions, and identify the starting seed voxel 220. To betterillustrate the starting seed voxel 220, the horizontal axis 225 and thevertical axis 230 are displayed in each of the three 2D slice images205, 210, and 215. The intersection of the horizontal axis 225 and thevertical axis 230 is the starting seed voxel 220. In an aspect, thestarting seed voxel 220 may be inside of the lung or a trachea and maybe determined manually or automatically. By selecting a seed voxel 220in the trachea the as the seed voxel 220, processes can be undertaken toquickly identify the airways within the lung from tissues outside of thelungs.

The trachea has a substantially constant diameter along its length. Inparticular, the upper part of the trachea extends substantially linearlyfrom the larynx and pharynx and behind the sternum. By using theseproperties of the trachea, the trachea may be found in the 2D sliceimages. Further details of finding the trachea to determine the startingseed voxel 220 is described in commonly assigned U.S. Provisional PatentApplication No. 62/020,253 entitled “Trachea Marking”, filed on Jul. 2,2014 by Lachmanovich et al.; and U.S. Provisional Patent Application No.62/020,257 entitled “Automatic Detection Of Human Lung Trachea”, filedon Jul. 2, 2014 by Markov et al.

After the starting seed voxel 220 is selected either manually orautomatically, a region growing algorithm is used to binarize the 2Dslice images. Based on the region growing algorithm, every voxel in theset of 2D slice images is checked to determine whether a Hounsfieldvalue assigned to each voxel is less than a threshold value and whethereach voxel is connected to the starting voxel 220. When it is determinedthat a value assigned to a voxel has a Hounsfield value less than thethreshold value and is connected to the starting seed voxel 220, theHounsfield value of the voxel is set to one or the maximum value.Otherwise, the Hounsfield value of the voxel is set to zero or theminimum value. As part of the region growing algorithm, the threshold isselected with a high enough value to cause leakage in the lung, and thusfill the lungs with intensity values leaked from the airways.

After every voxel in the set of 2D slice images is set to the maximum orminimum value, the 2D slice images will have only 2 colors of pixels.The result is a set of 2D slice images where the voxels/pixels havingthe maximum Hounsfield value would appear white, and the voxels/pixelshaving the minimum Hounsfield value would appear black. As shown in FIG.2B, in some instances, the values of voxels in the set of 2D sliceimages, and thus the pixels in the 2D slice images, are inversed so thatthe lung regions are shown in black and the non-lung regions are shownin white or another color.

FIG. 3 shows three 2D slice images 335, 340, and 345 depicting theresults of the segmentation and binarization with the lung tissueclearly depicted in grey on a background of the chest and othernon-airway or lung tissues in white. Though not yet complete, the viewsof FIG. 3 substantially identify the pleural boundaries of the lungs.

Since the lung has a porous structure, most of voxels of the binarizedset of 2D slice images representing the lung and the airways are shownin black. Some airway tissue (e.g., 355 in FIG. 3) having a Hounsfieldvalue greater than the threshold, however, will be shown in white.Further, voxels of the binarized 3D volume outside of the lung may alsobe shown in white because they are not connected to the starting seedvoxel 220 and have the maximum intensity value. Indeed any tissue havinga Hounsfield value above the threshold (e.g., voxel 350), will be shownas white.

The segmented, binarized, and inversed set of 2D slice images maycontain large black regions, which cover the lung. In an aspect, thethreshold value may be adjusted to make the large black regions as largeas possible to cover the pleural boundaries of the lungs with sufficientaccuracy. By decreasing the threshold value, voxels representing wallsof small airways or blood vessels appear in white and at the same time,the large black regions become smaller. On the other hand, when thethreshold value is increased, the walls of small airways and bloodvessels may not appear in white and the large black regions becomelarger. Thus, the threshold values may be adjusted to a value so thatwalls of airways and blood vessels, having a certain size, appear in inwhite and so that the large black regions grow as large as the pleura ofthe lungs.

The binarized, segmented and inversed set of 2D slice images may beviewed in the axial, coronal, and sagittal directions. FIGS. 4A and 4Bshows binarized 2D slice images for filtering out connected components,as well as filtered out 2D slice images, in accordance with anembodiment of the present disclosure. The three 2D slice images 405,410, and 415 are black and white images. The black region 420 representsthe lung, while white region represents areas outside of the lung andalso some connected components, such as blood vessels and walls ofairways, in the lung. These connected components are shown as smallwhite areas 435 in the 2D slice images 410 and 415.

Filtering out connected components starts from detecting connectedcomponents in each 2D slice image. Connected components are displayed aswhite regions in the large black regions, which represent the lung. Whenthe connected components are detected, an area of each connectedcomponent is calculated. In a case where a calculated area is less thana threshold value, the corresponding connected component is filteredout, meaning that pixels in the corresponding connected component arereassigned to zero. In other words, the corresponding connectedcomponent is merged into the lung area or the large black regions. Afterall connected components in the 2D slice image have been filtered out, afiltered out 2D slice image 405 along the axial direction is obtained.The filtered out 2D slice image 405 includes large black regions 420,whose boundaries define the pleural boundary of the lungs.

FIG. 4B includes filtered out 2D slice images 440, 450, and 460 alongthe axial, coronal, and sagittal directions, respectively. Afterfiltering out connected components in all the 2D slice images, eachfiltered out 2D slice image has large black regions as shown in thefiltered out 2D slice images 440, 450, and 460. These filtered out 2Dslice images are reassembled to generate a segmented set of 2D sliceimages, which includes black regions defining the pleural boundaries ofthe lungs. These black regions also define or restrict spaces fordiagnosis of and/or surgeries to the lungs. This pleural boundarydefining set of 2D slice images may be incorporated into pathwayplanning and treatment software such as the iLogic software sold byCovidien LP for diagnosis and treatment of the lungs of a patient. Theclear definition of the pleural boundaries can be used to partition thelungs from the surrounding tissue, and thereby used to create the 3Dvolume of the patient's lungs.

FIGS. 5A-5C show flowcharts of a segmentation method 500 for generatinga segmented set of 2D slice images defining the pleural boundaries of alung, in accordance with an embodiment of the present disclosure. Thesegmentation method 500 starts from step 505, in which CT scan imagedata of the chest of a patient is obtained, for example from a CTscanner. In an aspect, the CT image data may be obtained from anotherimaging modality, such as radiography, tomogram produced by a CAT scan,MRI, ultrasonography, contrast imaging, fluoroscopy, nuclear scans, andPET.

In step 510, the CT scan image data is processed to generate a set of 2Dslice images of the patient's chest. The set of 2D slice images mayinclude the lung, the pleura, the trachea, the heart, the stomach, andany other organs in the chest. A voxel is defined as the intersection ofthree 2D slice images viewed in the three directions, e.g., the axial,sagittal, and coronal directions. Each voxel has a value representingthree pixels, each of which is from a corresponding 2D slice image amongthe three 2D slice images viewed in the three directions. Segmentationof the set of 2D slice images of the chest starts by determining a seedvoxel 220 in the set of 2D slice images, and distinguishes a regionincluding the starting seed voxel from an area not including thestarting seed voxel. In step 515, the starting seed voxel is determinedautomatically or manually. The starting seed voxel may be located at aninside area of the trachea or of the lung. When the trachea is used todetermine the starting seed voxel, methods for automatically finding atrachea can be found in commonly assigned U.S. Pat. No. 9,754,367entitled “Trachea Marking”, filed on Jun. 29, 2015 by Lachmanovich etal.; and U.S. Pat. No. 9,836,848 entitled “System And Method ForSegmentation Of Lung”, filed on Jun. 30, 2015 by Markov et al., theentire contents of both of which is incorporated by reference. Afterfinding the trachea, any voxel inside of the trachea may be determinedas the starting seed voxel.

In step 520, a region growing algorithm is applied to process the set of2D slice images. The region growing algorithm is used to connect morevoxels to the seed voxel to grow the region containing the starting seedvoxel. This region may be used to determine the borders of the lung atthe end of the segmentation method 500.

By applying the region growing algorithm, each voxel of the set of 2Dslice images is binarized, that is, it has its Hounsfield value comparedto a threshold and reassigned to two colors, black and white. Blackvoxels represent the lung region and white voxels represent the non-lungregion. After the step 520, a new binarized set of 2D slice images isgenerated. Details of the step 520 is further described with referenceto FIG. 5B below.

In step 525, all 2D slice images are processed to filter out connectedcomponents therein. Connected components may represent blood vessels andwalls of airways having a Hounsfield value greater than the thresholdidentified above. Connected components are displayed as white areaswithin the lung area in 2D slice images. By filtering out or removingthe white areas having a size smaller than a predetermined thresholdfrom within the lung area, an area covering the lung may be displayedonly in black and the 2D slice images are prepared for determining thepleural boundaries of the lungs. Detailed descriptions for the filteringout process are provided with reference to FIG. 5C below.

After the filtering out process, in step 540, the processed set of 2Dslice images may be used to identify the pleural boundaries of thelungs. The segmentation method is ended after step 540. By performingthe binarization and connected component analysis on the 2D slice imageswith a minimum size limitation, the true boundaries, particularly thepleural boundaries are clearly defined for the clinician. Alternatively,instead of using the original CT scan image data, the 2D slice imagesused for process 500 may be generated from a different dataset. Anexample of another potential dataset to be used for process 500 is a setof 2D slice images generated based on a 3D model which was generatedbased on the original CT scan image data. Such a 3D model may present asmoother view of the patient's lungs with any gaps, omissions, and/orimperfections in the CT scan image data filled in or corrected. FIG. 5Bshows a flowchart illustrating step 520 of FIG. 5A, i.e., applying theregion growing algorithm to voxels of the set of 2D slice images of thepatient's chest. In step 521, an intensity (Hounsfield value) of a voxelof the set of 2D slice images is compared with a threshold value.

When it is determined that the intensity of the voxel is greater than orequal to the threshold value, step 524 follows, and otherwise step 522follows. In step 522, connectedness between the voxel and the startingseed voxel is determined. Here, connectedness ensures that the voxel isin the same region as the starting seed voxel, or in other words, thevoxel is in the lung region. This is done by considering the surroundingvoxels and determining whether they satisfy the same threshold criteria.This process is continued back to the starting seed voxel. Statedanother way, when there is a pathway from the voxel to the starting seedvoxel and the pathway is made up of a series of adjacent voxelssatisfying the threshold criteria, then the voxel is consideredconnected to the starting seed voxel. When it is determined that thevoxel is connected to the starting seed voxel, the intensity value ofthe voxel is assigned to the maximum value in step 523. The result is abinary mask of voxel intensities, with all connected voxels satisfyingthe threshold criteria having one assigned intensity value and allothers having another intensity value.

In an aspect, voxels, which are considered as seed voxel candidates,directly adjacent to a seed voxel may be compared with the thresholdvalue recursively without considering connectedness. This recursionmethod starts by comparing voxels adjacent to the starting seed voxeland recursively proceeds in all directions. In this case, checking forconnectedness is unnecessary.

When it is determined that the intensity of the voxel is not less thanthe threshold value in step 521, or that the voxel is not connected tothe starting seed point in step 522, the intensity of the voxel isassigned to the minimum value in step 523. In steps 523 and 524, the setof 2D slice images are segmented, resulting in voxels having only theminimum value or the maximum value.

Step 525 follows after the steps 523 and 524. In step 525, it isdetermined whether there remain voxels which have not been processedthrough the region growing algorithm. When there is such a voxel, steps521-525 are repeated until there are no more unprocessed voxels. Theresult of steps 521-525 is a binarized set of 2D slice images which onlyincludes black voxels for non-lung regions and white voxels for lungregions. In step 526, the assigned value of each voxel is inversed fromthe maximum to the minimum or from the minimum to the maximum so thatthe lung regions have black voxels and the non-lung regions have whitevoxels. In an aspect, the threshold value used in step 521 may beadjusted to cause sufficient leakage (e.g., a high intensity region) inthe lung region such that the high intensity region may cover the lungand the borders of the lung. In another aspect, the threshold value isgreater than or equal to the intensity value of the seed voxel.

FIG. 5C shows a flowchart for step 525 of FIG. 5A, i.e., filtering outconnected components from the 2D slice images, in accordance with anembodiment of the present disclosure. Step 525 starts from step 526,i.e., detecting a connected component in a 2D slice image generated fromthe binarized set of 2D slice images. The connected component mayrepresent a blood vessel and/or a wall of airways. In step 527, it isdetermined whether a connected component is detected. If it isdetermined that the connected component is not detected in step 527, thefiltering out step 525 goes to step 531 to check whether there are more2D slice images to detect connected components.

When it is determined that a connected component is detected in step527, an area of the detected connected component is calculated in step528. The area may be a number of pixels in a white area representing theconnected component.

In step 529, the calculated area is compared with a threshold value.When it is determined that the calculated area is greater than or equalto the threshold value, it goes back to step 526. That means theconnected components may not be a blood vessel or a wall of airways.When it is determined that the calculated area is less than thethreshold value, in step 530, the connected component is filtered out orremoved. In other words, pixels in the connected components are assignedto the minimum value. In result, the connected component is merged intothe large black regions covering the lung and the pleura.

In step 531, it is determined whether there are more 2D slice images tobe processed. When it is determined that there is an unprocessed 2Dimage, steps 526-530 are repeated to filter out connected components inthe unprocessed 2D slice image. Otherwise, the filtering out step 525 iscomplete.

In an aspect, the filtering out step 540 may process 2D slice imagestaken along one direction and process 2D slice images taken alonganother direction. For example, step 540 processes 2D slice images takenalong the axial direction first and other 2D slice images taken alongthe coronal direction and the sagittal direction in order. In anotheraspect, step 540 may process 2D slice images one by one without anyorder.

By binarizing the set of 2D slice images and filtering out connectedcomponents in the 2D slice images, the resulting set of 2D slice images,which is the segmented set of 2D slice images, may be used to determinethe pleural boundaries of the lungs, which may be used during either theplanning or navigation phases of an ENB procedure. For example, thisinformation may be useful during a planning phase to identify when asuspected target is located outside of the lungs. Alternatively, duringa procedure, this information can be used to notify the clinician when atool is approaching the pleural boundaries. In both instances awarenessof the location of the pleural boundaries assists the clinician inavoiding complications such a pneumothorax and other conditions whichmay occur as the clinician considers or approaches targets at or nearthe boundaries of the lungs.

Returning now to FIG. 1, memory 120 includes application 122 such as EMNplanning and procedure software and other data that may be executed byprocessors 110. For example, the data may be the CT scan image datastored in the DICOM format and/or the 3D model generated based on the CTscan image data. Memory 120 may also store other related data, such asmedical records of the patient, prescriptions and/or a disease historyof the patient. Memory 120 may be one or more solid-state storagedevices, flash memory chips, mass storages, tape drives, or anycomputer-readable storage media which are connected to a processorthrough a storage controller and a communications bus. Computer readablestorage media include non-transitory, volatile and non-volatile,removable and non-removable media implemented in any method ortechnology for storage of information such as computer-readableinstructions, data structures, program modules or other data. Forexample, computer-readable storage media includes random access memory(RAM), read-only memory (ROM), erasable programmable read only memory(EPROM), electrically erasable programmable read only memory (EEPROM),flash memory or other solid state memory technology, CD-ROM, DVD orother optical storage, magnetic cassettes, magnetic tape, magnetic diskstorage or other magnetic storage devices, or any other medium which canbe used to store desired information and which can be accessed by device100.

Display 130 may be touch-sensitive and/or voice-activated, enablingdisplay 130 to serve as both an input device and an output device.Graphics processors 140 may be specialized graphics processors whichperform image-processing functions, such as processing the CT scan imagedata to generate the 3D model, and process the 3D model to generate the2D slice images of the 3D model in the various orientations as describedabove, as well as the 3D renderings of the 3D model. Graphics processors140 may further be configured to generate a graphical user interface(GUI) to be displayed on display 130. The GUI may include views showingthe 2D image slices, the 3D rendering, among other things. Inembodiments, graphics processors 140 may be specialized graphicsprocessors, such as a dedicated graphics processing unit (GPU), whichperforms only the image processing functions so that the one or moregeneral processors 110 may be available for other functions. Thespecialized GPU may be a stand-alone dedicated graphics card, or anintegrated graphics card.

Network interface 150 enables device 100 to communicate with otherdevices through a wired and/or wireless network connection. In anembodiment, device 100 may receive the CT scan image data from animaging device via a network connection. In other embodiments, device100 may receive the CT scan image data via a storage device, such as adisk or other external storage media known to those skilled in the art.

Input interface 160 is used for inputting data or control information,such as setting values, text information, and/or controlling device 100.Input interface 160 may include a keyboard, mouse, touch sensor, camera,microphone, or other data input devices or sensors used for userinteraction known to those skilled in the art.

In addition, reference is made to following commonly assignedapplications: U.S. Pat. No. 10,772,532 entitled “Real-Time AutomaticRegistration Feedback”, filed on Jul. 2, 2015, by Brown et al.; U.S.Pat. No. 9,727,986 entitled “Unified Coordinate System for Multiple CTScans of Patient Lungs”, filed on Jul. 1, 2015, by Greenburg.; U.S.Provisional Patent No. 10,159,447 entitled “Alignment CT”, filed on Jul.2, 2015, by Klein et al.; U.S. Provisional Pat. No. 9,633,431 entitled“Fluoroscopic Pose Estimation”, filed on May 29, 2015, by Merlet.; U.S.Patent Application Publication No. 2016/0000520 entitled “System AndMethod Of Providing Distance And Orientation Feedback While NavigatingIn 3d”, filed on Jul. 2, 2015, by Lachmanovich et al.; and U.S. Pat. No.9,603,668 entitled “Dynamic 3D Lung Map View for Tool Navigation Insidethe Lung”, filed on Jun. 26, 2015, by Weingarten et al., the entirecontents of all of which are hereby incorporated by reference. All ofthese references are directed to aspects of modifying and manipulatingthe DICOM images to provide enhanced clarity and performance foranalysis, diagnostic, and treatment systems relating to, among otherthings, lung treatment planning and navigation.

Although embodiments have been described in detail with reference to theaccompanying drawings for the purpose of illustration and description,it is to be understood that the inventive processes and apparatus arenot to be construed as limited thereby. It will be apparent to those ofordinary skill in the art that various modifications to the foregoingembodiments may be made without departing from the scope of thedisclosure.

1-16. (canceled)
 17. A system for determining pleural boundaries of alung, comprising: a processor configured to: apply a region growingprocess to a first slice image of a set of 2D slice images to form agrown region, the region growing process starting with a seed voxelwithin a trachea and using a threshold value, wherein the region growingprocess includes: in a case where an intensity of a first voxel in thefirst slice image from the set of 2D slice images is lower than thethreshold value and the first voxel is connected to the seed voxel,setting the intensity of the first voxel as a maximum value; and in acase where an intensity of a second voxel in the first slice image fromthe set of 2D slice images is not lower than the threshold value or thefirst voxel is not connected to the seed voxel, setting the intensity ofthe second voxel as a minimum value; filter connected components of alung in each slice image of a set of binarized 2D slice images generatedfrom the grown region; and identify the pleural boundary of the lungbased on the set of binarized 2D slice images; and a display operablycoupled to the processor and configured to display a three-dimensionalrendering or a two-dimensional image of the lung.
 18. The systemaccording to claim 17, wherein the threshold value is greater than orequal to an intensity of the seed voxel.
 19. The system according toclaim 17, wherein the set of 2D slice images is stored in digitalimaging and communications in medicine (DICOM) image format.
 20. Thesystem according to claim 17, wherein the processor is furtherconfigured to: generate the set of 2D slice images based on acquiredimage data of a patient's chest; and determine the seed voxel in thetrachea connected to the lung in the first slice image of the set of 2Dslice images.
 21. The system according to claim 17, wherein thethreshold value causes a high intensity area to appear around the seedvoxel in the set of 2D slice images.
 22. The system according to claim17, wherein the processor is configured to filter connected componentsof the lung by: detecting a plurality of connected components in the setof binarized 2D slice images; calculating an area of each connectedcomponent in the set of binarized 2D slice images; determining whetherthe area of each connected component is less than a predetermined value;assigning a minimum value to pixels of a first connected component ofthe plurality of connected components when it is determined that an areaof the first connected component is less than the predetermined value;and assigning a maximum value to pixels of a second connected componentof the plurality of connected components when it is determined that anarea of the second connected component is greater than or equal to thepredetermined value.
 23. The system according to claim 22, wherein eachconnected component is an enclosed area with high intensity.
 24. Thesystem according to claim 22, wherein one or more of the plurality ofconnected components are blood vessels or airways.
 25. The systemaccording to claim 22, wherein an intersection of three 2D slice images,each of which is from each of three independent directions, identifies avoxel in the set of 2D slice images.
 26. The system according to claim25, wherein the three independent directions are axial, coronal, andsagittal directions.
 27. The system according to claim 17, wherein eachvoxel of the set of binarized 2D slice images has either high or lowintensity.
 28. The system according to claim 17, wherein the set of 2Dslice images is acquired from at least one of computed tomographictechnique, radiography, tomogram produced by a computerized axialtomography scan, magnetic resonance imaging, ultrasonography, contrastimaging, fluoroscopy, nuclear scans, and positron emission tomography.29. A non-transitory computer-readable storage medium storinginstructions which, when executed by a processor, cause the processorto: apply a region growing process to a first slice image of a set of 2Dslice images to form a grown region, the region growing process startingwith a seed voxel within a trachea and using a threshold value, whereinthe region growing process includes: in a case where an intensity of afirst voxel in the first slice image from the set of 2D slice images islower than the threshold value and the first voxel is connected to theseed voxel, setting the intensity of the first voxel as a maximum value;and in a case where an intensity of a second voxel in the first sliceimage from the set of 2D slice images is not lower than the thresholdvalue or the first voxel is not connected to the seed voxel, setting theintensity of the second voxel as a minimum value; filter connectedcomponents of a lung in each slice image of a set of binarized 2D sliceimages generated from the grown region; and identify a pleural boundaryof the lung based on the set of binarized 2D slice images.
 30. Thenon-transitory computer-readable storage medium according to claim 29,wherein the threshold value is greater than or equal to an intensity ofthe seed voxel.
 31. The non-transitory computer-readable storage mediumaccording to claim 29, wherein the set of 2D slice images is stored indigital imaging and communications in medicine (DICOM) image format. 32.The non-transitory computer-readable storage medium according to claim29, wherein the instructions, when executed, further cause the processorto: generate the set of 2D slice images based on acquired image data ofa patient's chest; and determine the seed voxel in the trachea connectedto the lung in the first slice image of the set of 2D slice images. 33.A system for determining pleural boundaries of a lung, comprising: aprocessor configured to: form a grown region by: setting an intensity ofa first voxel in a first slice image of a set of 2D slice images as amaximum value in a case where an intensity of the first voxel in thefirst slice image from the set of 2D slice images is lower than athreshold value and the first voxel is connected to a seed voxel withina trachea; and setting the intensity of a second voxel in the firstslice image from the set of 2D slice images as a minimum value in a casewhere an intensity of the second voxel in the first slice image from theset of 2D slice images is not lower than the threshold value or thefirst voxel is not connected to the seed voxel; filter connectedcomponents of a lung in each slice image of a set of binarized 2D sliceimages generated from the grown region; and identify the pleuralboundary of the lung based on the set of binarized 2D slice images. 34.The system according to claim 33, wherein the threshold value is greaterthan or equal to an intensity of the seed voxel.
 35. The systemaccording to claim 33, wherein the processor is further configured to:generate the set of 2D slice images based on acquired image data of apatient's chest; and determine the seed voxel in the trachea connectedto the lung in the first slice image of the set of 2D slice images. 36.The system according to claim 33, wherein the processor is furtherconfigured to inversely assign values of voxels in the set of 2D sliceimages, from the minimum value to the maximum value and from the maximumvalue to the minimum value, to obtain the set of binarized 2D sliceimages.